$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
4.76
\begin{equation} \begin{gathered}\label{equation:minimal-is-mono} \xymatrix@R =50pt@C=50pt{ \sigma _0 \ar [rr]^-{ \operatorname{id}} \ar [dr]_{\alpha (\sigma _0)} & & \sigma _0 \\ & (G \circ F)(\sigma _0) \ar [ur]_{\beta (\sigma _0)} & } \end{gathered} \end{equation}